NOTE: The list below refers to what had been done to the car through the 2001 season primarily for competition in Street Prepared. Since then I've made a few more changes and have noted them at the end of each section if appropriate. I've also tried to remember to indicate modifications I've made for Street Modified, which is the class I competed in at the 2003 and 2004 Solo II Nationals.
Also, all the modifications I've listed below were legal for the class I was in at the time I posted them. However, the SCCA Solo Rules continually change and I can't promise that all the modifications I've listed will be legal in any particular class forever, so please review the current rules (available at SCCA.com) for your class before making any modification to your car.
A lot of people have asked me what I've done to our 1995 M3 to make it so competitive in SCCA autocross competition. At first our car appears to be virtually stock since it doesn't have wildly flared fenders and monster tires and wheels.
Too often people confuse "doing everything you can do" to a car with "doing what actually works best" on a car. I do a lot of testing to learn the latter and avoid the former.
Here's the straight skinny on what I have and have not done to our car. Get out the No-Doz and read to your heart's content.
I run a 3.38 diff out of the M3 automatic in the car and have since early in the 1999 season. The 3.38 does help a bit coming out of corners but also shortens 2nd gear to only a 57mph top speed. On most ProSolo courses that's not a problem, but on fast Solo II courses I'm faced with riding the rev limiter or using 3rd a lot. (On the South course at the 2000 Solo II Nationals I was forced to shift to 3rd in two different places.)
I ran a 3.23 final drive (out of a 97 M3) in 1998. Although it allows a 60 mph top speed in 2nd gear, I saw little improvement over the stock 3.15 (which allows 62 mph in 2nd). I actually switched back to the 3.15 after the '98 ProSolo Finale and before the Solo II Nats because of the course design. (Kevin Bailey helped with the swap as my feeble upper body strength wasn't quite up to the task.)
To maintain the optimal torque "sweet spot" without running out of revs on a typical Solo II course might require traveling to all events with all three diffs and installing the one that best suits the course for the day. It's "only" about a two hour job. Although most would consider that level of prep nuts, I did exactly that at Nationals in 1998. I arrived with the 3.15 in the car, but put the 3.23 in when I saw how tight the ProSolo course was. Then reinstalled the 3.15 for the Solo II Nationals because the courses were much more open.
I'm now convinced the 3.38 is faster than either the 3.23 or 3.15, but it requires up and down shifting on many courses.
I still run the stock exhaust manifold. I've tried a couple different racing headers and neither produced as much torque on the dyno as the OE manifold. And torque is what wins autocrosses.
Last year I started running a FlowMaster cat-back exhaust that I had designed for the 97 (3.2l) M3 I roadraced in '98 and love it. Dyno results show modest gains in peak horsepower (+7hp) and torque (4-7 lb/ft), but I believe its greatest benefit to be in weight savings -- it weighs only 21 pounds.
2003 update: I am now running a full header-back exhaust system with a high-flow cat and Magnaflow muffler. Dyno tests show no significan gain (+/-1hp) but by replacing the OE cats with a single high-flow unit and going to a single 3" pipe all the way from the headers, I've now saved 37 pounds of excess weight. And it's perfectly legal in Street Prepared as well as Street Modified.
2004 update: I am now using a Turner Motorsports "shorty" headers along with a Tunnell Race Products full header-back exhaust system with a Magnaflow muffler and no cat. We've yet to hit the dyno, but preliminary acceleration tests are very encouraging.
Now that Hoosier produces their popular 285/30/18 tire in the autocross compound, I'm no longer faced with the choice of having to go to a much taller tire to get a little additional width. So I had a set of wheels custom made by Complete Custom Wheel with the greatest possible offset to give me the narrowest possible track, which I believe is a big advantage in autocross situations.
I also recently flared the fenders to allow the use of this new tire and am very pleased with the results. In very cold weather I'm confident the 245 would still be the tire size of choice and I have yet to do any back to back testing, but results so far have been very positive.
A/C in the car -- yep, still in there. That's the most valuable extra 40 pounds on the car. When it's 95 degrees outside and everyone else is wilting from the heat, I stay cool, calm, and collected and I *know* I can perform to the best of my personal abilities.
2003 update: I've changed my position slightly on this. I still believe staying cool, calm, and collected prior to competition is critcailly important, but now I've got a wonderful truck to cool off in if needed. So for the National Championships in 2002 I removed the a/c for the first time in a desperate attempt to save weight. Fortunately, Nationals week was not very hot so the a/c wasn't missed. I decided to leave it out for the 2003 season and so far I've been able to stay cool in the truck and keep the car as light as possible.
For those not fighting for a ProSolo or Solo II National Championship, I'd definitely advise leaving the a/c alone.
WEIGHT (fact, not fantasy)
How much does an M3 weigh? Well, it varies. I weigh mine at almost every event and I can tell you that on most scales our car weighs +/- 2930 with 1/4 tank of fuel. That's with 13-pound Recaro seats (driver and passenger) replacing the stock LTW seats (64 pounds each), aluminum flywheel (11 vs 24 pounds), Forgeline wheels (17.5 vs 23.5 pounds each), and custom exhaust (21 vs. 51 pounds).
In AS trim our car weighed 3123 at 1996 Solo II Nats.
2003 update: In SM trim our car weighed 2798 at the 2003 Wendover ProSolo thanks to a light weight battery, removal of the rear seat and trailer hitch, and lighter exhaust. After installing a carbon fiber hood from MA Shaw we trimmed the weight to just over 2770 at Nationals.
In 197-98 I ran Koni double-adjustable Sport shocks and strut inserts (same as I ran in AS), H&R 29910 Sport springs, and custom camber plates I designed and had fabricated by Precision Machine Werks.
In 1999 and 2000 I ran JRZ triple-adjustable coilover shocks with remote reservoirs, combined with H&R 60mm race springs (450lb front and rear) and TC Kline Design camber/caster plates which permit from -1.5 to -4.25 degrees negative camber. The car has a nearly perfect 50-50 weight balance.
In 2002 I switched from JRZ triple-adjustables to Moton triple-adjustables and raised the front spring rate to 90 nM (515#).
I use the BMW factory chassis "x-brace" which triangulates both sides of the lower portion of the transmission tunnel for added stiffness. This brace comes standard on all M3 convertibles, the M3 LTW, and all Z3's.
Racing Dynamics anti-sway bars, 27mm front and 22mm rear ,with urethane bushings and links with spherical ball joint ends. I ran stock anti-sway bars in 1997-98.
2004 update: I have switched to H&R's 28mm front and 24mm rear sway bars and love them. Their unique bushings bonded with Teflon-impregnated fabric are ZERO maintenance.
I use an aluminum Fidanza flywheel weighing 12 pounds (stock weighs 24 pounds) to reduce rotating driveline mass.
Red Line Oil in the engine, Red Line D4-ATF in the tranny, and Mobile One 75W90 synthetic gear lube in the diff.
2004 update: We have switched to using Mobile One 5W40 in the engine and BMW Synthetic ATF in the transmission. No complaints with the Red Line fluids... we've had excellent results with the Mobile One oil and the BMW trans fluid offers slightly smoother shifting.
Amoco 93 octane at sea level and Amoco 91 in Denver.
NGK BCP6EV gold fine-wire spark plugs developed by Secret Ignition.
2003 update: I've switched to NGK BKR6EIXA iridium fine-wire plugs. Same performance range as the gold plugs, but longer duty cycle.
In July the K&N FilterCharger air filter was replaced with a Conforti/Eurosport Cold Air Intake with ITG air filter. I thought my Euro airbox with K&N filter was good, but I am very impressed with the performance of the new system. A very cost-effective upgrade.
Recaro "SPG" fiberglass driver and passenger seat with Recaro sliders mounted on TC Kline Design mounting brackets.
Momo "Champion" 350mm wheel with hub.
Forgeline RS 17" x 9" ET40 with H&R 15mm spacers in front.
2002 update: To take advantage of Hoosier's new 245/35/18 autocross tire I switched to SSR Integral 18" x 9" ET45 wheels with additional 5mm spacers front and back.
2003 update: To take advantage of Hoosier's new 285/30/18 autocross tire I switched to Complete Custom 18" x 10" front and 18" x 10.5" rear wheels.
Hawk HP+ brake pads. Stock rotors and calipers, no ducting.
Stable Technologies non-telescoping harness bar for mounting shoulder harness and video camera mount.
(No lectures, please, on the dangers of using a harness bar.)
Pyrotect 3" lap and shoulder belts with cam-lock release for both driver and passenger.
DynaBatt racing battery (13 lbs.) in the stock location.
2003 update: Switched to a Hawker Odyssey battery using a Russ Wiles battery box in the stock location. The Hawker batter has greatly improved battery terminals and costs a bit less to boot.
You can order a Russ Wiles Battery box and battery here.
else is there?
I use a Simpson open face helmet, Oakley shoes, drink Gatorade, and always wear my lucky red underwear.
2004 update: Two words: gray jockies.
WITH THE M3 LTW?
Lots of myths and legends abound, but here's what I know about them.
In reality most LTW's weigh roughly 200 pounds less than a comparably equipped "standard" M3 -- a rare one with no sunroof, LTW interior (like mine), etc. Most of that savings was due to the aluminum door skins, and the lack of A/C or any serious undercoating or sound deadening. (Click here to see Jeff Lloyd's post about M3 LTW specs.)
A standard M3 equipped with sunroof, leather interior, A/C, CD player, etc. could easily weigh 400 pounds more than a zero-option LTW. But most were about 200-250 pounds more than most of the std. M3's on the road.
Considering the mods allowed in Street Prepared, I would expect a similarly prepared LTW would weigh about 3.5% less (100 lbs) less than mine.
LTW motors came off the same production line as other M3 motors, but all M3 motors are dyno'd prior to installation and the strongest 10% were reserved for LTW cars and motorsports sales. So the motors in LTW's were hand-picked, not really hand-built as many believe.
PS. If you have any specific questions about my car, feel free to write me.